Railway traffic controlling apparatus



May 2, 1944.

R. M. LAURENSON RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Sept. 5, 1942 n Rm w M W N Aw m mLiA m? Patented May 2, 1944 RAILWAY TRAFFIC CONTROLLING APPARATUS Robert M. Laurenson, Elkhart, Ind., assignor to. The Union Switch and Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application September 5, 1942, Serial No. 457,443

. 3 Claims.

My invention relates to railway traflic controlling apparatus, and it has particular referenoe to the organization of such apparatus into railway traflic controlling systems of the class employing coded track circuits arranged to provide approach control without use of line wires. More particularly, my invention relates to the approach control portion of such apparatus.

It has been proposed heretofore to govern aproach controlled functions by means of a slow releasing repeater relay which is energized over a circuit including a front contact of an auxiliary track relay. The auxiliary track relay is pro vided at the exit end of a track section and is connected across a resistor interposed in the circult over which coded energy is applied to the rails of the section. The circuit constants are so selected that when the section is unoccupied, the major portion of the battery voltage appears across the track rails and only a slight voltage drop appears across the resistor. Under these conditions, the auxiliary relay is released and remains so until a train enters the section and establishes a low resistance path across the track rails. As the train advances into the section and shunts out more and more of the track rails resistance, the voltage drop in the resistor gradually increases to a value sufficient to enable the auxiliary relay to pick up. It has been found that as the voltage applied to the auxiliary relay increases, this relay starts to code, that is, it picks up and then releases, first with a very short picked-up time which gradually increases to a normal picked-up time as the voltage becomes increasingly large. Each time the auxiliary relay picks up, it closes its front contact to energize the repeater relay which in turn picks up, but due to the initially short picked-up time of the auxiliary relay, the energy in the repeater relay winding at first does not reach a value suificient to enable this relay to bridge the release periods of the auxiliary relay. This results in a coding action of the repeater relay and an intermittent energization of the approach controlled functions. Such intermittent energization is undesirable, particularly in the case where signals are approach illuminated since it results in a blinking or flashing of such signals.

In view of the foregoing and other considerations, it is an object of my present invention to provide means for improving the operation of the approach control apparatus to prevent intermittent energization of the approach controlled functions.

Another object is the provision ofnovel and.

improved means for preventing coding action of a repeater relay energized over a front contact of a relay that is picked up and released alter-- nately for varying intervals.

A further object is the provision, in a system of the type described, of an auxiliary source of energy for the repeater relay to assist in holding such relay in its picked-up position during relatively long deenergized periods. 7

In practicing the invention, the above-mentioned and other important objects and charac teristic features of my invention which will be-- come readily apparent from the following description, are attained by means of a capacitor which has an energizing or charging circuit ineluding a back contact of the repeater relay and which is connected in circuit with the repeater relay over its own front contact.

I shall describe one form of apparatus embodying my invention and shall then point out the novel features thereof in claims.

The accompanying drawing is a diagrammatic view showing one form of apparatus embodying my invention,

Referring to the drawing, the reference characters I and la designate the track rails of a stretch of railway track divided by insulated joints 2 into a plurality of successive adjoinin track sections of which only one section, D--E. is represented complete'in the drawing. Traflic normally moves over the stretch in the direction indicated by the arrow or from left to right as viewed in the drawing, and is governed by signals S positioned at the entrance ends of the sections.

The signals S are governed by means of suitable decoding apparatus, indicated conventionally in the drawing by the reference character DA, each arranged to establish an energizing circuit for one or another of a plurality of lamps of the associated signal according to the code rate of operation of a track relay provided for the associated section. Track relay TR, for example, is incorporated into a track circuit provided for section DE and comprising relay TR connected across the rails at the entrance end I) of the section, and a track circuit source of energy, such as a battery TB, connected across the rails at the opposite end of the section over a path including a resistor 5, and a front contact 6 of a code transmitter or coder CT.

Coder CT is arranged to intermittently open and close its front contact 6 and thereby supply to the track rails coded current consisting of on and "off intervals during which energy is and is not applied to the rails, respectively.-

nal B of a suitable source of current, such as a battery not shown, through front contact I of relay VR and the winding of relay VM to the other terminal C of the source of current, When repeater relay VM is released, its back point of contact 8 is closed and a capacitor 9 is then connected to the source of energy through a current limiting resistor I0. When relay VM is picked up, the front point of its contact 8 connects capacitor'9 and resistor l0 across the terminals of the winding of relay VM', thereby providing a discharge circuit for the capacitor.

Relay VM functions as an approach control relay. As here shown, a front contact ll of this relay is included in the circuit for the decoding apparatus DA for signal S at location E.

The apparatus is adjusted so thatwith section DE vacant, the major portion of the potential of battery TB appears across the track rails l and .la each time contact 6 of coder CT is closed, and this potential causes relay TR to operate at the same rate as coder CT. Relay VB is at this time released since the voltage drop across resistor is insufficient to cause the relay to pick up.

'When, however, a train enters section DE and establishes a low resistance path across the rails, relay TB is shunted and remains released, while a larger portion of the voltage of battery TB is consumed in resistor 5. This voltage continues to increase as the train proceeds further into the section and shunts out more of the track rail resistance, and the apparatus is adjusted so that when the train reaches a predetermined point in the section, say about 4,000 feet from its exit end, the voltage across resistor 5 reaches the value sufficient to pick up relay VR. At this time the voltage is quite marginal and the energy level in the relay is slow to build up, hence the relay picks up just before the end of each on interval of energy, and maintains its front contact closed for but a slight time interval. These time intervals increase in duration quickly as the train travels nearer to its exit end, until relay VR, operates in synchronism with the operation of coder CT and closes its front contact forthe full duration of each of the on intervals of the code.

The slow releasing approach control relay VM, if energized only over a front contact of relay VR, would pump or follow the coded action of relay VR when that relay first begins to follow code and closes its front contacts for the short on time intervals. This action of relay VM would result from the fact that at this time relay VR, holds its front contact I closed for an interval long enough for relay VM to pick up but too short to enable the energy level in that relay to build up to the value sufficient to hold the relay in its picked-up position during each of the relatively long intervals that contact 1 of relay VB is open.

To obviate this pumping or coding action of relay VM, capacitor 9 is provided. This capacitor is charged to the potential of the source, indicated by the reference characters B and C, when relay VM is released. Thus, when relay VM picks up in response to the first closure of contact I of relay VR, capacitor 9 is connected through the front point of contact 8 to the winding of relay VM, and discharges through that winding to hold up that relay until front contact 1 of relay VR again closes. When this happens, relay VM again becomes energized from the source B-C and capacitor 9 is again charged with energy from the same source. During-the subsequent intervals in which contact I is open, the capacitor discharges through the winding of relay VM to hold it in its picked-up position. 'This operation of the apparatus is maintained until the train vacates section DE and removes its shunt on the track rails. When this happens, relay TR again operates, relay VR releases and relay VM also releases to open its front contact H and deenergize the lamps of signal SE.

From the foregoing, it is readily apparent that I have provided means whereby a capacitor may be utilized as an energy storing device to supply energy to a repeater relay during the intervals that the energizing circuit for the repeater relay is interrupted. In this connection, .it is to be noted that the initial charge of the capacitor effected over the back point of contact 8 of relay VM is highly important since this enables the condenser to become fully charged and hence provides a large amount of stored energy to be available to energize relay VM when it first picks up. This feature distinguishes the circuit arrangement from that employing a condenser connected permanently across the relay terminals, since in the latter arrangement the condenser is normally discharged and can accept a charge for only the short interval during which the front contact of relay VB. is closed. This latter arrangement has been found to be unacceptable since it does not eliminate the coding action of relay VM, whereas the circuit involving a back contact of the relay has been found to be wholly satisfactory in eliminating such coding action.

Although I have herein shown and described only one form of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with a control relay that may be picked up and released alternately for variable lengths of time. a condenser, a second relay, a source of current, a normally closed charging circuit for said condenser including said source of current and a back contact of said second relay, an energizing circuit for said second relay including in series a front contact of said control relay and'a winding of said second relay and said source of current, and a discharge circuit for said condenser comprising a front contact and the said winding of said second relay.

2. In combination with a control relay that may be picked up and released alternately for variable lengths of time, a second relay, a capacitor, a source of energy, a normally closed charging circuit for said capacitor including said source of energy and a back contact of said second relay, an energizing circuit for said second relay including in series a front contact of said control relay and a winding of said second relay and said source of energy, and a branch circuit path including a front contact of said second relay for connecting said capacitor to said energizing circuit in muitiple with the said winding of said second relay.

3. The combination with a track circuit comprising a track relay connected across the rails at one end of a track section and a source of current intermittently connected through a re sistor to the rails at the opposite section end, an approach control relay connected across said 

